Spell stored as higher-level versions of themselves are not upcast
When a spell is stored by default as a higher-level version of itself (e.g. fireball as a fifth-level), it is cast as if it were the standard-level version (e.g. a fireball stored as a fifth-level spell rolls damage as if it were cast at third level). This can be problematic as some items only store higher-level versions of some spell (e.g. a staff of power only holds the fifth-level version of Lightning bolt and Fireball).
Spell upcasting does work as intended (damage and charge cost is increased), so this is a different issue.